Final answer:
DNA polymerase uses a proofreading mechanism to ensure accurate base pairing during DNA replication, with an exonuclease activity that removes incorrectly paired bases. Additional repair mechanisms, including mismatch repair, further increase the fidelity of DNA replication.
Step-by-step explanation:
How DNA Polymerase Ensures Accurate Nucleotide Selection
DNA polymerase is integral in maintaining the accuracy of DNA replication. The enzyme has a proofreading ability, whereby it reads the newly added nucleotide to confirm it has correctly paired with the template strand. If a mismatch is detected, the DNA polymerase performs a cut at the phosphodiester bond via its 3' exonuclease action, releasing the incorrect nucleotide. Afterward, the correct nucleotide is inserted, ensuring high fidelity in DNA replication. Besides proofreading, other mechanisms such as mismatch repair work to correct errors that slip past the initial replication process, further bolstering the accuracy of DNA replication.
Mispaired bases that manage to escape the proofreading process can be corrected post-replication by mismatch repair enzymes. In bacteria like E. coli, the parental DNA strand is distinguished by methylation, allowing repair enzymes to recognize and excise the mismatched base only from the newly replicated strand, ensuring the integrity of the genetic material. For the occasions where proofreading and mismatch repair may fail, cells have additional damage repair mechanisms to minimize mutations and maintain genetic stability.